Ureter

The ureters enter the bladder from its back surface, traveling 1.5–2 cm (0.6–0.8 in) before opening into the bladder at an angle on its outer back surface at the slit-like ureteric orifices.[2]^[3] This location is also called the vesicoureteric junction.^[4] In the contracted bladder, they are about 25 mm (1 in) apart and about the same distance from the internal urethral orifice; in the distended bladder, these measurements may be increased to about 50 mm (2 in).^[2]

A number of structures pass by, above, and around the ureters on their path down from the kidneys to the bladder.

The arteries that supply the ureters end in a network of vessels within the adventitia of the ureters.^[1] There are many connections (anastamoses) between the arteries of the ureter,^[2] particularly in the adventitia,^[5] which means damage to a single vessel does not compromise the blood supply of the ureter.^[2][5] Venous drainage mostly parallels that of the arterial supply;^[5][2] that is, it begins as a network of smaller veins in the adventitia; with the renal veins draining the upper ureters, and the vesicular and gonadal veins draining the lower ureters.^[1]

Lymphatic drainage depends on the position of lymphatic vessels in the ureter.

The ureters are richly supplied by nerves that form a network (plexus) of nerves, the ureteric plexus that lies in the adventitia of the ureters.^[2] This plexus is formed from a number of nerve roots directly (T9-12, L1, and S2-4), as well as branches from other nerve plexuses and nerves; specifically, the upper third of the ureter receives nerve branches from the renal plexus and aortic plexus, the middle part receives branches from the upper hypogastric plexus and nerve, and the lower ureter receives branches from the lower hypogastric plexus and nerve.^[2] The plexus is in the adventitia. These nerves travel in individual bundles and along small blood vessels to form the ureteric plexus.^[2] Sensation supplied is sparse close to the kidneys and increases closer to the bladder.^[2]

Sensation to the ureters is provided by nerves that come from T11 - L2 segments of the spinal cord.^[2] When pain is caused, for example by spasm of the ureters or by a stone, the pain may be referred to the dermatomes of T11 - L2, namely the back and sides of the abdomen, the scrotum (males) or labia majora (females) and upper part of the front of the thigh.^[2]

Microanatomy

The ureter is lined by

The ureters develop from the ureteric buds, which are outpouchings from the mesonephric duct. This is a duct, derived from mesoderm, found in the early embryo.^[8] Over time, the buds elongate, moving into surrounding mesodermal tissue, dilate, and divide into left and right ureters. Eventually, successive divisions from these buds form not only the ureters, but also the pelvis, major and minor calyces, and collecting ducts of the kidneys.^[8]

The mesonephric duct is connected with the cloaca, which over the course of development splits into a urogenital sinus and the anorectal canal.^[8] The urinary bladder forms from the urogenital sinus. Over time, as the bladder enlarges, it absorbs the surrounding parts of the primitive ureters.^[8] Finally, the entry points of the ureters into the bladder move upwards, owing to the upward migration of the kidneys in the developing embryo.^[8]

Function

The ureters are a component of the urinary system. Urine, produced by the kidneys, travels along the ureters to the bladder. It does this through regular contractions called peristalsis.^[2]

• 
  Ultrasound showing a jet of urine entering the bladder (large black section) through the ureter.

Clinical significance

Ureteral stones

A

Most stones are compounds containing

Cancer

squamous cell carcinoma if the type of cells lining the urethra have changed due to chronic inflammation, such as due to stones or schistosomiasis.^[18]

Investigations performed usually include collecting a sample of urine for an inspection for malignant cells under a microscope, called

tumour grade, with a worse prognosis associated with an ulcerating lesion.^[18]

Injury

Injuries to the ureter can occur after penetrating abdominal injuries, and injuries at high speeds followed by an abrupt stop (such as a high speed car accident).

abdominal hysterectomies,^[20] usually near the suspensory ligament of the ovary or near the cardinal ligament, where the ureter runs close to the blood vessels of the uterus.^[21]

Imaging

Several forms of medical imaging are used to view the ureters and urinary tract.

retrograde pyelogram is where dye is injected into the urinary tract via a catheter, and flows backwards into the ureters.^[22] More invasive forms of imaging include ureteroscopy, which is the insertion of a flexible endoscope into the urinary tract to view the ureters.^[23] Ureteroscopy is most commonly used for medium to large-sized stones when less invasive methods of removal cannot be used.^[23]

Other animals

All

ventral to the vas deferens in male placental mammals, but dorsal to the vas deferens in marsupials.^[27]

History

The word "ureter" comes from the Ancient Greek noun οὖρον, ouron, meaning "urine", and the first use of the word is seen during the era of Hippocrates to refer to the urethra.^[28] The anatomical structure of the ureter was noted by 40 AD. However, the terms "ureter" and "urethra" were variably used to refer to each other thereafter for more than a millennium.^[28] It was only in the 1550s that anatomists such as Bartolomeo Eustachi and Jacques Dubois began to use the terms to specifically and consistently refer to what are in modern English called the ureter and the urethra.^[28] Following this, in the 19th and 20th centuries multiple terms relating to the structures such as ureteritis and ureterography, were coined.^[28]

Kidney stones have been identified and recorded about as long as written historical records exist.^[29] The urinary tract including the ureters, as well as their function to drain urine from the kidneys, has been described by Galen in the second century AD.^[30]

The first to examine the ureter through an internal approach, called ureteroscopy, rather than surgery was

fiber optics, which occurred in 1964.^[29] The insertion of a drainage tube into the renal pelvis, bypassing the ureters and urinary tract, called nephrostomy, was first described in 1941. Such an approach differed greatly from the open surgical approaches within the urinary system employed during the preceding two millennia.^[29]

The first

intravenous urogram, in which contrast is injected into a vein and highlights the kidney and, when excreted, the urinary tract.^[31] Things improved with the development by Moses Swick and Leopold Lichtwitz in the late 1920s of relatively nontoxic contrast media, with controversy surrounding publication as to who was the primary discoverer.^[31] Side-effects associated with imaging improved even more when Tosten Almen published a ground-breaking thesis in 1969 based on the less toxic low-osmolar contrast media, developed based on swimming experiences in lakes with different salinity.^[31]

References

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17. ^ R, Martin; Baker, H (14 October 2019). "Nursing care and management of patients with a nephrostomy". Nursing Times.
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